[R-390] The adventure begins (and a capacitor question).

[John Saeger]

----- Original Message -----
From: "Barry Hauser" <barry@hausernet.com>
To: "John Saeger" <john@whimsey.com>; <R-390@mailman.qth.net>
Sent: Tuesday, May 21, 2002 7:04 PM
Subject: Re: [R-390] The adventure begins (and a capacitor question).

[snip...]


>
> Whaddya mean "line audio stuff" -- the meter?/ranges?

Well the meter doesn't do anything when I flip the switch, and the line gain
doesn't seem to do anything.  Of course I don't have anything hooked up to
the line output, but I sort of expected the meter to do something.

>
> > Sounds great through a Klipsch Heresy.
>
> That's a good start -- you're lucky so far.  "Heresy" -- is that the right
> model name?  Does it defy accepted acoustical engineering practice?  Or is
> the name something like "Heritage"?  BTW, you are using a 600/8 ohm
> transformer, right?


It's the right model name.  Paul Klipsch was famous for his speaker designs
the most famous of which is the Klipschorn, which has become a cultural icon
in a way that is similar to the R-390 series.  Although it's probably been
exceeded by some extremely expensive modern speakers, it was a *best in
class* design for a long time.  He used horns even for the bass which match
the acoustic impedance of the speaker driver to the air much more
efficiently than traditional speaker designs.  This gets you much more
loudness for much less amplifier output.  Although the Klipschorn has
massive power handling capacity, some people like to drive them with single
ended tube amps with only a couple of watts of output.  Plenty of volume.  I
think the Heresy got it's name because it has a more traditional woofer.  It
still has horns for the midrange and tweeter though.  But overall it's less
efficient than the original Klipschorn.  And yes, I'm using a Rad-Shack 70V
line transformer.

>
>   A vintage speaker that's too ugly
> > for my living room.
>
> No -- probably more like your living room is not appropriately decorated.
> How many 6 foot rack cabinets?  Droplight sconces?  Neon beer signs?

Nooooo, I don't have beer signs in my living room.  ;-)

>
>   So the overpriced shipping may have worked out.
> >
> > It's a little bit moody though.
>
> What do you mean by moody?

Most of the time it's just great.  But sometimes it fades out with a
crackly, buzzy sound.  I'm not completely convinced it's a capacitor or a
tube yet.  It could be a bad pot or switch.  At first I thought it might be
the RF gain pot but now I'm suspecting a flakey contact in the band switch.
If it starts crackling I seem to be able to make it go away by changing
bands and coming back.  But I'm not sure.

[snip...]

>   So it may be possible to replace all of the papers with ceramics.  But I
> don't know if
> > it's a good idea.  What do you guys think?
>
> Not recommended.  Later built SP-600's came through with mostly ceramic
> disks, but not the cap of choice for R-390A's in most cases.

I wish I knew why.  But I don't have a problem with using the orange drops,
since they are known to work well.  Something interesting I saw while
cruising the AVX web site.  They make some ceramics that are big.  Many
microfarads.  So I'm toying with the idea of trying to get some of those to
replace the electrolytics with.  We'll see...

> I'd replace that one cap right away before you burn out the filters.
> Unlikely, but you've been too lucky so far.
>
> Some things to check -- try all bands, using the calibrator if necessary
or
> a siggen.  It's not uncommon to find some are dead -- usually come in 2's
> and 3's according to the crystal configuration scheme.  Some of the xtal
> decks have rather loose sockets, so get out the DeOxit and do those, tube
> sockets and pins, any switches you can reach -- and later on the ones you
> can't reach ;-).  Check all the tubes, especially for shorts.  Check the
> gear train for grit, gluey grease.  Oh -- with the top off and the "utah"
> cover removed, very carefully watch the slug racks as you change bands and
> tune through.  Some may be binding on the downstroke.  It's sometimes
> difficult to see and you have to press lightly on a rack that's supposed
to
> be going down to see if it isn't hanging up.  Also make sure the cam
> follower rollers are actually rotating otherwise you'll be flat-spotting
> them as you tinker around.
>
> Other basic preliminaries -- check the two plugin caps on the audio deck.
> Check the mechanical synch using the procedure in the manuals.  Look for
any
> broken or loose clamps.  Check the range on the KC control end to end.
> There are a lot of preliminaries that would logically come before a total
> recap job, at least from where I sit.
>
> This is one radio where there's lots to do and look at before listening.
> But that's the fun.  Just be careful if someone casually asks "Whatcha
doin'
> John?" and you answer "Watchin' the radio."  They might take you away.
> (There are a number of guys on this list that are unaccounted for. ;-)

More great ideas.  Thanks!

John